Peristaltic pumps are well-known devices which transfer fluid through an elongate flexible tube by compressing a portion of the tube, and pushing the fluid through the tube using such compression. Peristaltic pumps are commonly used for transferring fluids such as ink for printing or for transferring fluids such as blood in medical equipment. Peristaltic pumps may also be used to transfer fluids such as cleaning agents, coolants, slurries or liquid adhesives, just to name a few of the many fluids that can be transferred with such pumps. One advantageous feature of peristaltic pumps is that the fluid does not contact the pump mechanism since the fluid is always confined within and moved through the flexible tube. Therefore, peristaltic pumps may be used to transfer corrosive or caustic solutions or other hazardous fluids without affecting the pump mechanism.
In a typical peristaltic pump, the tube is compressed by one or more rollers that are driven by an electric or air-powered motor. Each roller compresses the tube as it moves along the length of the tube. Also typically, the flexible tube is fed through the pump along a generally U-shaped path or alternatively along a substantially straight arc-shaped path (in the case of a pass-through pump) so that the U-shaped or arc-shaped portion of the tube overlaps a portion of a path traveled by the rollers. Such arrangements have numerous disadvantages. For example, the tube can undesirably creep through the pump during operation of the pump, requiring either periodic adjustment of the tube, or a separate clamping device to prevent such creep of the tube. A U-shaped or substantially straight arc-shaped tube path in a peristaltic pump provides a small contact area between the pump rollers and the tube, as the rollers are only in contact with the tube over a small portion of the overall path of travel of the rollers. As a result, depending on the flow rate requirements imposed on the pump, there can be substantial fatigue imposed on the tube. The use of additional rollers may partially correct this problem, but causes additional wear on the tube and adds cost and complexity to the pump.
In many peristaltic pumps using a U-shaped tube path, the flexible tube is oriented such that the fluid flowing into the pump flows in a direction opposite to that of the fluid flowing out of the pump. In such an arrangement, additional space and tube length is required if the pump is to be disposed along a line leading from the source of fluid directly to the destination to which the fluid is being pumped, as the tube must turn 90.degree. to enter the pump and the tube must also turn 90.degree. to exit the pump. As will be appreciated, these turns could also cause kinking of the flexible tube that would either interrupt or at least interfere with the free flow of fluid. Such kinking is highly undesirable and could be dangerous in some applications.
The housing of a typical peristaltic pump as well as the components located within the housing can be complex and expensive to manufacture, especially if a large number of rollers are used in the pump. Therefore, there is a need for a peristaltic pump that is economical to manufacture, durable, compact and capable of reliably and efficiently pumping fluid.